As a device for detecting an electric leakage (ground fault) of a power source unit using an AC generator as a power source, there is proposed an electric leakage detection system wherein an electric leakage is detected by detecting a zero-phase current flowing through a ground line which connects a neutral point of armature coils of a three-phase AC generator to ground, as disclosed in Japanese Patent Application Laid-Open Publication Nos. 10-142282 and 2000-149758.
In such an electric leakage detection system for detecting an electric leakage from a zero-phase current flowing through a ground line which grounds a neutral point of a generator when the electric leakage occurs, it is necessary to lay around the long ground line which grounds the neutral point of the generator to a place of installation when it is required to install the electric leakage detection system apart from the generator, and thus complexity for distributing the ground line was a problem.
In addition, when there is not a neutral point among the armature coils of the AC generator, for example, a case where the armature coils are delta-connected or the generator is a single-phase AC generator, a proposal described above cannot be applied.
In order to take a required step when the electric leakage occurs, it is desirable to be able to determine a position where the electric leakage (ground fault) occurred in the power source unit. However, determination of a position of the electric leakage cannot be performed in a conventional electric leakage detection system.